Detecting charged particle events at high dose rates

Abstract

Charged particle microscope (CPM) support systems and apparatus, as well as related methods, computing devices, and computer-readable media. One charged particle microscope support apparatus includes first logic to detect a first charged particle event at a first pixel of a charged particle camera, and second logic to detect, within a subregion of pixels of the charged particle camera containing the first pixel, whether a second charged particle event is present based on a dose rate and an energy value of each pixel within the subregion of pixels. When the second charged particle event is determined to be present, the second logic determines a location of the second charged particle event within the subregion. The support apparatus further includes third logic to output charged particle event data representing the first charged particle event and the second charged particle event.

1 . A charged particle microscope support apparatus, comprising:
 first logic to detect a first charged particle event at a first pixel of a charged particle camera;   second logic to determine, within a subregion of pixels of the charged particle camera containing the first pixel, whether a second charged particle event is present based on a dose rate and an energy value of each pixel within the subregion of pixels and, when the second charged particle event is determined to be present, determine a location of the second charged particle event within the subregion of pixels; and   third logic to output charged particle event data representing the first charged particle event and the second charged particle event.   
     
     
         2 . The charged particle microscope support apparatus of  claim 1 , wherein the second logic determines the location of the second charged particle event based on a second pixel within the subregion of pixels having a sub-maximum energy value, the sub-maximum energy value being a maximum of energy values within the subregion of pixels excluding the energy value of the first pixel. 
     
     
         3 . The charged particle microscope support apparatus of  claim 1 , wherein the second logic determines whether the second charged particle event is present by:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel, and   determining that the second charged particle event is present based on the probability determined for each pixel within the subregion of pixels.   
     
     
         4 . The charged particle microscope support apparatus of  claim 1 , wherein the second logic determines whether the second charged particle event is present by:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel,   determining a probability total by adding a minimum probability within the subregion of pixels and a maximum probability within the subregion of pixels, and   determining that the second charged particle event is present in response to the probability total being greater than a predetermined threshold.   
     
     
         5 . The charged particle microscope support apparatus of  claim 4 , wherein the predetermined threshold is set based on the dose rate. 
     
     
         6 . The charged particle microscope support apparatus of  claim 1 , wherein the subregion of pixels includes a square area of 3 to 5 pixels. 
     
     
         7 . A charged particle microscope, comprising:
 a support apparatus, including logic to:   detect a first charged particle event at a first pixel of a charged particle camera;   determine, within a subregion of pixels of the charged particle camera containing the first pixel, whether a second charged particle event is present based on a dose rate and an energy value of each pixel within the subregion of pixels;   when the second charged particle event is determined, determine a location of the second charged particle event within the subregion of pixels; and   output charged particle event data representing the first charged particle event and the second charged particle event.   
     
     
         8 . The charged particle microscope of  claim 7 , wherein the support apparatus determines the location of the second charged particle event based on a second pixel within the subregion of pixels having a sub-maximum energy value, the sub-maximum energy value being a maximum of energy values within the subregion of pixels excluding the energy value of the first pixel. 
     
     
         9 . The charged particle microscope of  claim 7 , wherein the support apparatus determines whether the second charged particle event is present by:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel, and   determining that the second charged particle event is present based on the probability determined for each pixel within the subregion of pixels.   
     
     
         10 . The charged particle microscope of  claim 7 , wherein the support apparatus determines whether the second charged particle event is present by:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel,   determining a probability total by adding a minimum probability within the subregion of pixels and a maximum probability within the subregion of pixels, and   determining that the second charged particle event is present in response to the probability total being greater than a predetermined threshold.   
     
     
         11 . The charged particle microscope of  claim 10 , wherein the predetermined threshold is set based on the dose rate. 
     
     
         12 . The charged particle microscope of  claim 7 , wherein the subregion of pixels includes a square area of 3 to 5 pixels. 
     
     
         13 . A method of supporting a charged particle microscope, comprising:
 detecting, with a processing device, a first charged particle event at a first pixel of a charged particle camera;   determining, with the processing device within a subregion of pixels of the charged particle camera containing the first pixel, whether a second charged particle event is present based a dose rate and an energy value of each pixel within the subregion of pixels;   when the second charged particle event is determined, determining, with the processing device, a location of the second charged particle event within the subregion of pixels; and   outputting, with the processing device, charged particle event data representing the first charged particle event and the second charged particle event.   
     
     
         14 . The method of  claim 13 , wherein the location of the second charged particle event is determined based on a second pixel within the subregion of pixels having a sub-maximum energy value, the sub-maximum energy value being a maximum of energy values within the subregion of pixels excluding the energy value of the first pixel. 
     
     
         15 . The method of  claim 13 , wherein determining whether the second charged particle event is present includes:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel, and   determining that the second charged particle event is present based on the probability determined for each pixel within the subregion of pixels.   
     
     
         16 . The method of  claim 13 , wherein determining whether the second charged particle event is present includes:
 determining, for each pixel within the subregion of pixels, a probability of a charged particle impinging the pixel,   determining a probability total by adding a minimum probability within the subregion of pixels and a maximum probability within the subregion of pixels, and   determining that the second charged particle event is present in response to the probability total being greater than a predetermined threshold.   
     
     
         17 . The method of  claim 16 , wherein the predetermined threshold is set based on the dose rate. 
     
     
         18 . The method of  claim 14 , wherein the subregion of pixels includes a square area of 3 to 5 pixels. 
     
     
         19 . The method of  claim 14 , wherein determining whether the second charged particle event is present includes:
 determining a probability for each pixel within the subregion of pixels based on a first histogram of energy values for single charged particle events and a second histogram of energy values for double charged particle events.   
     
     
         20 . The method of  claim 14 , further comprising:
 generating the first histogram by detecting charged particle events in a low dose image, defining a first blob for each detected charged particle event, and adding the energy value of a center of each blob to the first histogram; and   generating the second histogram by expanding each first blob into a second blob, combining random pairs of blobs to generate combined blobs, wherein each random pair of blobs includes one of the first blobs and one of the second blobs, and adding an energy value of a center of each combined blob to the second histogram